1. Field of the Invention
The present invention relates to a thin DC-DC converter arrangement and more particularly, to a thin DC-DC converter arrangement which supplies stable DC power to a load of electronic equipment.
2. Description of the Related Art
As electronic device is made smaller in weight and size, its power supply has been made smaller in size and particularly in thickness. Most electronic devices are designed to operate not only on public power source but also on battery. In such an electronic device, a DC-DC converter is built in a power source port of the electronic device to convert unstable DC power into a desired stable DC voltage and then supply the DC voltage to a load. A DC voltage obtained by converting an AC voltage of a public power source by an AC adapter or a DC voltage supplied from a battery is generally not good in stability and accuracy.
Recently, DC-DC converters have been designed in an on-board type that is mounted on a circuit board of the main body. The on-board type DC-DC converter generally has a plurality of pins on its lower side which are connected by soldering to an electric circuit of the main body formed on a rear side of the circuit board of the main body through through-holes previously made in the main body circuit board.
As a conventional example of the on-board type DC-DC converter, there is known a converter having a structure such that a circuit board is fixedly mounted on one surface of a radiating fin and a supporting member having a drum type inductor (choke coil) fixed by caulking thereto is fixedly mounted on the other surface of the radiating fin (for example, refer to JP-U-2-82008, "Transistor Technology", 26 (1989) 6, p 497). This example, as in a general 3-terminal regulator, can be operated by adding electrolytic capacitors to its input and output.
This DC-DC converter is disadvantageous in making the converter smaller in size and low in leakage flux, because the converter uses a drum type inductor. That is, since the drum type inductor uses a drum type sintered ferrite core on which a coil is wound, the miniaturization has its limit. Further, because the converter uses the supporting member, it has been difficult to make the converter smaller in size and thickness. In addition, since the core of the drum type inductor for providing its magnetic circuit is not made in closed loop, much magnetic flux has leaked. The leakage flux causes misoperation of ICs or a circuit of an electronic device or generation of beat when inductors of DC-DC converter are mounted to be facing to each other, resulting in difficulty in making the electronic device smaller in size.